Suitability of GaP nanoparticles as a surface-assisted laser desorption/ionization mass spectroscopy inorganic matrix and their soft ionization ability

Abstract

Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF-MS) using GaP nanoparticles (NPs) prepared by a gas evaporation method was investigated on poly(ethylene glycol)s (PEGs). The mass spectra of PEG and survival yield measurements suggested that larger GaP NPs have a quite high soft ionization ability.

Mechanisms of Nanophase-Induced Desorption in LDI-MS. A Short Review

“…Similar argumentation can explain, for instance, the reduced laser threshold (see Figure 4) needed to desorb 4-chlorobenzylpyridinium (BP-Cl) ions using yellow GaP nanoparticles of size smaller than red GaP NPs [39]. …”

“…The investigation of the nature of interactions arising when pulsed laser radiation hits a nanostructure is an almost unexplored field in LDI-MS. More frequently, microscopy techniques (e.g., atomic force microscopy—AFM, scanning electron microscopy—SEM) have been applied for the characterization of LDI nanostructured substrates, before and after laser irradiation [39,54,69,77,79,105,106]. However, “in situ” techniques as well as theoretical modelling would be important to study the process.…”

“…In this respect, the majority of the studies dealing with SALDI-MS applications, invoked the thermal-driven desorption (via laser-induced heating) [5,58,60] and heat confinement [48,54,57] as fundamental mechanisms, though other non-thermal mechanisms (e.g., phase transition [51,53,58,62], analyte-NP interactions [51,57,58]) may contribute to the overall LDI process. It is, therefore, often difficult to assess which physicochemical factor plays the most prominent role, as mutual and simultaneous contributions occur [39,42,48,54,57,58]. Chemical composition and size of NPs are certainly key features, as the final physicochemical properties of the nanomaterials will strongly depend on them.…”

“…Moreover, the dependence of the SYs on the laser fluence could help in assessing the “softness” (i.e., reduced, or even null, fragmentation) of the LDI process and/or to shed light on desorption mechanisms and underlying influential factors [39,61,65,66,67]. CNTs, C 60 and PGC exhibited similar high SYs at laser fluencies in the range 20 mJ cm −2 –40 mJ cm −2 (Figure 2a), indicating that poor fragmentation occurs on these substrates [57].…”

“…Further, recently explored hybrid systems such as gold nanoparticles (AuNPs) supported on silicon plate with cationic copolymer [34], iron oxide nanoparticles modified with sinapic acid [35] or magnetic NPs coupled to TiO 2 [36], SiNWs functionalized by Ag nanoparticles [37,38], would not be included as well. Lately, Yonezawa et al [39] divided SALDI-MS techniques into two categories: (i) nanostructured surfaces such as commercially available DIOS, NALDI, Quickmass, and (ii) nanoparticle systems including diverse inorganic nanoparticles or combination of them. Tarui et al [34] distinguished “wet” (referring to ultrafine, nanometer- and micrometer-sized, metal particles suspended in glycerol and other liquids) from “dry” SALDI, which includes a large variety of materials such as carbon nanotubes, metal nanoparticles, porous silicon and alumina.…”